This application is to study effector choice in parietal-frontal circuits. It focuses on movement plans and decisions regarding which part of the body to use to obtain a goal. Although this is a very common behavior and important for daily activities such as typing, playing musical instruments, sports, and operating an automobile, to our knowledge effector choice has generally not been studied at the neuronal level. Aim 1 will examine 2 models of cortical processing for effector selectivity. The parallel model hypothesizes that all cortical areas that represent potential movement plans before selection are the same areas that represent the outcomes of those decisions. The serial model hypothesizes that some cortical areas represent potential plans and outcomes and later cortical areas only represent the outcomes. Aim 2 will examine the dorsal premotor cortex (PMd) to see if it is similar to the parietal reach region (PRR) in representing both potential plans and outcomes. It will also determine whether PMd cells are mostly selective for reach outcomes (like PRR) or if it contains a mixture of reach and saccade selective neurons. The latter finding would suggest that PMd may be further along in the pathway for hand-eye coordination than PRR, which is suggested by other recent studies examining coordinate frames. Although PRR and the lateral intraparietal area (LIP) have recently been found to have activity consistent with their representing potential plans and outcomes of effector decisions, there is no evidence that they are actually necessary for effector decision making. Aim 3 will test whether LIP and PRR are necessary by inactivating them during effector decision making. If inactivation of these two areas produce a bias in the decision task (LIP for saccades and PRR for reaches), then these areas would be within the network for effector decision making. The three aims will provide important new information regarding how effector planning and decisions are processed including the functional hierarchy of the areas involved (Aim 1), the role of dorsal premotor cortex (Aim 2), and whether areas in the parietal cortex are involved in the decision process or only reflect the potential plans and the outcome of the decision (Aim 3).

Public Health Relevance

Results from this study can be used to help design therapies for patients suffering from damage to frontal and parietal cortex from strokes and traumatic brain injuries. They will help in understanding deficits that result from neurological diseases that effect cortical functioning, and in guiding diagnoses and treatments for these diseases. They will also be useful for guiding the design of neural prosthetics. By determining the types of signals that can be obtained from different brain regions, neural implants can be made to read out these signals in order to control assistive external devices for paralyzed patients.